On Mon, Jun 27, 2011 at 4:41 PM, shantharam balasubramanian <
shantharam...@gmail.com> wrote:
> Hi
> I am new to python and I need to know about adding new blocks.
> I modified the benchmark_tx and rx.py files, so that the receiver will
> get the file from sender and store it in a txt file which is passed as
> an arguement. I also added few lines of code so that the receiver
> calculates the number of error bits in each packet it receives.
>
> The program is as follows:
> #!/usr/bin/env python
> #
> # Copyright 2005,2006,2007,2009 Free Software Foundation, Inc.
> #
> # This file is part of GNU Radio
> #
> # GNU Radio is free software; you can redistribute it and/or modify
> # it under the terms of the GNU General Public License as published by
> # the Free Software Foundation; either version 3, or (at your option)
> # any later version.
> #
> # GNU Radio is distributed in the hope that it will be useful,
> # but WITHOUT ANY WARRANTY; without even the implied warranty of
> # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> # GNU General Public License for more details.
> #
> # You should have received a copy of the GNU General Public License
> # along with GNU Radio; see the file COPYING. If not, write to
> # the Free Software Foundation, Inc., 51 Franklin Street,
> # Boston, MA 02110-1301, USA.
> #
>
> from gnuradio import gr, gru, modulation_utils
> from gnuradio import usrp
> from gnuradio import eng_notation
> from gnuradio.eng_option import eng_option
> from optparse import OptionParser
>
> import random
> import struct
> import sys
> import time
> import binascii
> # from current dir
> import usrp_receive_path
> import operator
> #import os
> #print os.getpid()
> #raw_input('Attach and press enter: ')
>
> class my_top_block(gr.top_block):
> def __init__(self, demodulator, rx_callback, options):
> gr.top_block.__init__(self)
> # Set up receive path
> self.rxpath = usrp_receive_path.usrp_receive_path(demodulator,
> rx_callback, options)
>
> self.connect(self.rxpath)
>
> #
> /////////////////////////////////////////////////////////////////////////////
> # main
> #
> /////////////////////////////////////////////////////////////////////////////
>
> global n_rcvd, n_right
>
> def main():
> global n_rcvd, n_right, bi, pattern, a, x, t, coun, tbin, i, l, abin
>
> n_rcvd = 0
> n_right = 0
> coun=l=0
> #FILE = open("payload.dat", "a")
>
> def rx_callback(ok, payload):
> global n_rcvd, n_right, coun, l
> (pktno,) = struct.unpack('!H', payload[0:2])
> n_rcvd += 1
> if ok:
> n_right += 1
>
> print "ok = %5s pktno = %4d n_rcvd = %4d n_right = %4d" % (
> ok, pktno, n_rcvd, n_right)
> a =ord(payload[2:options.size])
> abin=bin(a)[2:]
> FILE.write(payload[2:options.size])
> #a=ord(payload[2:options.size])
> print ('a = ' , a)
> print('abin=',abin)
> x =ord('a')
> #print('x=b=', x)
> t= operator.xor(a,x)
> #print("t=", t)
> tbin= bin(t)[2:]
> #print('tbin= ',tbin)
> i=0
> l=len(abin)+l
>
> while i<len(tbin):
> if tbin[i]=='1':
> coun=coun+1
> i=i+1
> print("total error bits so far=",coun)
> print("total bits=", l)
> b=float(coun)/float(l)
> print("b=",b)
> demods = modulation_utils.type_1_demods()
>
> # Create Options Parser:
> parser = OptionParser (option_class=eng_option,
> conflict_handler="resolve")
> expert_grp = parser.add_option_group("Expert")
>
> parser.add_option("-m", "--modulation", type="choice",
> choices=demods.keys(),
> default='gmsk',
> help="Select modulation from: %s [default=%%default]"
> % (', '.join(demods.keys()),))
> parser.add_option("-s", "--size", type="eng_float", default=1500,
> help="set packet size [default=%default]")
>
> usrp_receive_path.add_options(parser, expert_grp)
>
> for mod in demods.values():
> mod.add_options(expert_grp)
>
> (options, args) = parser.parse_args ()
>
> filename = args[0];
> FILE = open(filename, "a")
>
> if len(args) != 1:
> parser.print_help(sys.stderr)
> sys.exit(1)
>
> if options.rx_freq is None:
> sys.stderr.write("You must specify -f FREQ or --freq FREQ\n")
> parser.print_help(sys.stderr)
> sys.exit(1)
>
>
> # build the graph
> tb = my_top_block(demods[options.modulation], rx_callback, options)
>
> r = gr.enable_realtime_scheduling()
> if r != gr.RT_OK:
> print "Warning: Failed to enable realtime scheduling."
>
> tb.start() # start flow graph
>
> tb.wait() # wait for it to finish
> FILE.close()
>
> if __name__ == '__main__':
> try:
> main()
> except KeyboardInterrupt:
> pass
>
>
> I am now trying to find the received signal power in receiver node and
> I found many websites mention this particulat piece of code to be
> added to the program:
>
> alpha = 0.001
> thresh = 30 # in dB, will have to adjust
> self.probe = gr.probe_avg_mag_sqrd_cf(thresh,alpha)
> self.power_sink = gr.file_sink(gr.sizeof_float, "rxpower.dat")
> self.connect(self.probe, self.power_sink)
>
> But I am unable to connect this probe to the rxpath. whenever i add code
> like:
>
> self.connect(self,self.probe) # connects the input block to
> the power probe
> self.connect(self.probe, self.rxpath)# connects the power block
> to the rece
>
> I get error like,
> ValueError: port number 0 exceeds max of (none)
>
> I think this is something related to the number of ports in some block
> am trying to connect. Can anyone help me with this?
>
The object self.rx_path is from the class receiver_path (in receive_path.py)
and has no outputs. You can see this in receive_path's io_signature line,
where the second line (the output) is set to 0.
What you can do, though, is connect an internal block from the receive path
to your probe. Such as self.rx_path.channel_filter.
Tom
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